Hydraulic drilling jar

ABSTRACT

A hydraulic well jar having a metering system and a spline system located in separate, fully enclosed constant volume chambers to minimize seal wear and to enable use of a hydraulic fluid in the metering system and a lubricating oil for the splines.

United I States Patent [72] Inventor Frank C. Love '5 Rgfgyn Cited Houston, Tex. UNITED STATES PATENTS [21] P 858325 2,690,226 9/1954 rComstock 175/297x [22] 1969 2 710 171 6/1955 Ba ell 175/297 Patented Mar. 2 a a 8 [73] Assignee Schlumberger Technology Corporation Primary Examiner-David H. Brown New York, N.Y. Attorneys-Ernest R. Archambeau, Jr., William J. Beard,

' David L. Moseley, Edward M. Roney and William R.

Sherman [54] HYDRAULIC DRILLING JAR 6Claims,3Drawing Figs. N WWW [52] U.S. 175/297, ABSTRACT: A hydraulic well jar having a metering system 175/306 and a spline system located in separate, fully enclosed con- [51] lnt.Cl .1 E2lb 1/10 stant volume chambers to minimize seal wear and to enable [50] Field of Search 175/296, use of a hydraulic fluid in the metering system and a lubricat- 297, 29 5, 294, 306 ing oil for the splines.

-. -17 ark'y '28 -Q3 l- 7 A B u:- 46 24 w-sf -22 L -36 Frank C. Love IN VE N TOR Z4 ATTORNEY PATENTED HAR 2 mm FIG. 28

FIG. 2A

HYDRAULIC DRILLING JAR This invention relates generally to jars used in loosening objects stuck in a well, and more specifically to a hydraulic drilling jar for freeing stuck pipe or the like and particularly adapted to withstand the severe service conditions normally encountered in drilling operations.

Hydraulic jars have been used for a number of years in fishing, coring and whipstocking operations. Such jars usually comprise tubular telescoping members having coengageable impact surfaces that can be brought together by manipulating the pipe string to deliver a violent blow'to an object that has become stuck inthe well. A piston arrangement in the jar acts to meter fluid in a controlled manner to retard relative movement over an initial portion of the jar stroke, enabling potential energy to be stored in the drill string by stretching it. Then the metering piston becomes inactive and the members can move freely relative to one another until the impact surface engage. The jar can be cycled repeatedly to deliver the blows necessary to drive the stuck object loose.

l-leretofore, however, the hydraulic jar has-not found particularly successful application as a'drilling jar'because of the extremely rugged conditions encountered in drilling operations. For example, a drilling jar must be able to withstand lengthy periods of service downhole and still remain operational. It is possible for a jar to remain in the well several weeks before a round trip for the pipe is needed to change bits, giving an opportunity to service the jar. Further, a drilling jar must be extremely rugged in order to withstand the torsion stresses and vibration inherent in drilling operations. Moreover, the circulating fluids in 'the well contain cuttings and other debris that can have adverse affects on jar seals during telescoping movement of the jar-parts. High temperature can also be a factor.

For the foregoing among other reasons, the industry has resorted primarily to mechanical jars for drilling operations, Although mechanical jars are quite rugged and do not require high pressure seals and the like, such jars are generally quite lengthy and heavy and are complex and costlyto manufacture and repair.

It is the principle object of the presentinvention to provide a new and improved hydraulic jar that is constructed and arranged to withstand the extreme conditions imposed upon it by drilling operations.

This and other objects are attained in accordance with the principles and concepts of the present invention by a jar comprising telescopically related inner and outer members adapted to be connected in the drill string and having splines for transmitting rotation during drilling. The members are relatively movable between contracted and extended positions to bring coengageable impact surfaces together to deliver a jarring blow to a stuck object. Movement toward extended position is retarded by a hydraulic metering piston that operates only over an initial portion of the travel to enable a stretch to the taken in the drill string. When the metering piston releases, one jar member is accelerated upwardly by the potential energy stored in the drill string to bring the impact surfaces together in a rather violent manner. According to one aspect of the present invention, the metering system and the splines are fully enclosed in separate chambers. The metering system chamber contains a hydraulic metering fluid chosen primarily for its ability to maintain a substantially constant viscoscity over a wide temperature range. The spline system chamber, on the other hand, is filled with gear oil or the like chosen primarily for optimum lubricating characteristics. Each system is provided with a pressure transfer piston to equalize fluid pressures with the hydrostatic pressure of fluids in the well bore. In accordance with another aspect of the present invention, the seals closing the chambers in a fluidtight manner are located on particular seal diameters such that each chamber maintains a constant volume during telescoping movement of the inner and outer members. Accordingly, there is no pumping action during telescoping movement tending to cause seal wear.

The present invention has other objects and advantages that will become more apparent in view of the following detailed description taken together with the accompanying drawings in which: 1

FIG. 1 is a longitudinal schematic view of the lower section of a drilled hole showing a drill string, jar and drill bit; and

FIGS. 2A and 2B are longitudinal sectional views, partly in side elevation, showing the constructional details of a jar in accordance withthe principles of the present invention, FIG. 28 forming a lower continuation of FIG. 2A.

Referring initially to FIG. 1, a well bore 10 is shown being drilled into the earth by a drill bit 11, according to well-known rotary drilling techniques, a number of drill collars 12 can be located immediately above the bit 11, to provide the desired weight thereon, and a jar 13 according to this invention is shown connected to the drill collars. If desired, additional drill collars 12' can be located above the jar 13, and a drill string 14 composed of many sections of drill pipe connected to endto-end relationship extends upwardly to the top of the borehole; Fluids are circulated down the drill string 14, jar l3 and drill collars 12 through the bit 11 and return to the surface through the annulus between the drill string and the borehole wall to lubricate the bitand carry away the cuttings.

Referring now to FIGS. 2A and 28', a jar according to the present invention is shown as comprising an inner mandrel assembly 15 telescopically disposed within an outer housing assembly 16. The upper end section 17 of the housing assembly 16 andthe lower end section 18 of the mandrel assembly 15 are adapted to be threadedly connected to the drill collars 12. The housing assembly '16 further includes an upper cylinder section 19 having stepped internal surfaces 20 and 2l,a seal section 22, and a spline section 23 having internal longitudinal splines 24. The mandrel assembly 15 includes an upper section 15 and a cylinder section 26 that is connected to a spline section 28 having external longitudinal splines 29that mesh with the splines .24 to slidably and corotatively couple the members together. When the mandrel and housing assemblies are telescoped together or contracted as shown in the drawings, an annular shoulder surface 30 on the upper end of the spline section 23 is spaced away from a downwardly facing shoulder surface 31 on the mandrel section 28. These surfaces are adapted to the brought together by upward movement of the housing assembly 16 relative to the mandrel assembly 15 in order to deliver a violent blow to the pipe connected below the mandrel assembly, and in this art the surface 30 is often referred to as the hammer while the surface 31 is called the anvil.

In order to retard relative upward movement of the housing assembly 15 over an initial portion of the stroke of the jar so that potential energy can be stored] in the drill string by stretching it, a metering system 32 is located within a closed chamber 34 between the mandrel assembly 15 and housing assembly 16. The chamber 34 is filled with hydraulic fluid as will be subsequently described. The lower end of the chamber 34 is closed off by suitable seal packing 36 that seal against the outer surface 37 of the mandrel section 26, whereas the upper end of the chamber is closed off by a floating balance piston 38. The balance piston 38 has inner and outer seals 39 and 40, the inner seal 39 engaging the outer periphery of the upper mandrel section 25 on the same seal diameter as the lower seal 36. A wiper ring 35 can be mounted on the section 25 to engage the inner wall of the housing section 17. The upper surface of the balance piston 38 is exposed by ports or the like to the hydrostatic pressure of fluids in the borehole, and functions to transmit that pressure to the hydraulic fluid filling the chamber 34. v

The metering assembly 32 comprises an annular valve sleeve 44 that is urged upwardly against an annular valve seat 45 by a coil spring 46, the valve seat being formed by an enlarged shoulder 47 on the mandrel section 25. The coil spring 46 can be located between two retainer rings 48 and 49, the lower ring being positioned on the mandrel section 26 by nuts 50 and 51.. A plurality of grooves 55 extend longitudinally of the mandrel between points adjacent the valve seat 45 to points located beyond the lower end of the valve sleeve 34. When the housing assembly 16 is in a lower position relative to the mandrel assembly is, the valve assembly 44 occupies a position within the smaller diameter bore section 56 of the cylinder section 1Q. The outer diameter of the valve sleeve 44 is slightly smaller than the inner diameter of the section 56 so that although there is a relatively snug fit, a small annular metering or leak passage is provided between the outer periphery of the valve sleeve 44 and the inner wall surface 20 of the section 56. Accordingly, when the housing assembly 16 is pulled upwardly relative to the mandrel assembly 15, the hydraulic fluid in the chamber 34 below the valve sleeve 44 is compressed and pressurized, causing it to leak past the valve sleeve and into the upper portion of the chamber 34. The

' greater pressure in the lower portion of the chamber maintains the valve sleeve 44 closed tightly against the seat 45, so that a slow metering action takes place. The retarding effect enables a stretch to be taken in the drill string. However, when the enlarged diameter bore section 57 is disposed opposite the valve sleeve 44, a large flow area is presented between the valve sleeve and the wall surface 21 so that the metering action is suddenly terminated. The housing assembly 16 will be accelerated upwardly relative to the mandrel assembly 15, bringing the hammer 30 against the anvil 31 in a violent manner.

To recock the jar, the housing assembly 16 is lowered by slacking off on the drill string, and the valve sleeve 44 will move downwardly against the force of the spring 46, so that hydraulic fluid can pass through the longitudinal grooves 55 in the mandrel section 26 and enable repositioning of the valve sleeve 44 within the small diameter bore section 56 of the cylinder 19. The jar can be cycled as many times as needed to free the stuck pipe.

A closed chamber 64 is also provided for the splines 24 and 29. Annular seal packing 65 engages the outer periphery 66 to close off the lower end of the chamber 64, whereas the upper end is closed by another floating balance piston 67 having inner and outer seals 68 and 69. The inner seal 68 seals against a surface 70 formed with same diameter as the surface 66 engaged by the seal packing 67. The upper face of the balance piston 67 is exposed to well fluid pressure via ports 71 to equalize pressures. The chamber 64 is filled with a suitable gear oil or the like selected primarily for its lubricating ability.

In operation, the jar 13' is assembled as shown in the drawings and coupled in the drill string to be lowered in the borehole 10. As previously mentioned, the upper chamber 34 is filled with hydraulic fluid, whereas the lower chamber 64 is filled with lubricating oil. During normal drilling, the jar 13 is in compression and the housing assembly 16 and mandrel assembly remain in contracted condition. Of course the splines 24 and 29 transmit torque. In the event that the bit 11 or the drill collars 12 below the jar should become stuck in the borehole, and upward strain is taken in the drill pipe 14. Upward force on the housing assembly 16 generates greater fluid pressure in the hydraulic fluid below the valve sleeve 44 than above it, so that the metering action as previously described takes place. When the valve sleeve 44.reaches the enlarged bore section 57 of the cylinder 19, relatively speaking, the housing assembly is suddenly released, so that the potential energy stored in the drill pipe can accelerate the housing assembly upwardly and cause the hammer 30 to strike the anvil 31 a violent blow. The housing assembly 16 can be lowered to recock the jar as previously described, and repetitive blows can be applied to the stuck pipe until it comes loose.

The complete enclosure of the splines 29 and 24 in a lubricating oil protected from the drilling fluids insures minimum wear and maximum service life for these parts. The enclosure of the splines Within a separate chamber from the hydraulic metering system enables the use of a good lubricating oil in the former, while an efficient hydraulic fluid having a substantially constant viscosity over a wide temperature range can be used in the later to insure a high degree of repeatability of jarring action. As those skilled in the art will appreciate, these two fluids are not efficiently interchangeable, however, the present invention accommodates the use of both.

Each enclosed system is balanced with hydrostatic fluid pressures so that these pressures can not work against the jar, and the location of the inner seal for each chamber on portions of the mandrel assembly having respectively the same diameters provides constant volume for each chamberduring telescoping movement of the housing and mandrel assemblies. This feature prevents any pumping action during use of the jar and prevents seal wear.

Since various modifications can no doubt be made by those skilled in the art to the embodiment shown in the drawings without departing from the concepts of the present invention, it is the aim of the appended claims to cover these modifications or changes within the true spirit and scope of the present invention.

1 claim:

1. A jar apparatus comprising: a mandrel member telescopically disposed within a housing member, said members being relatively movable between extended and contracted positions; means for connecting said members in a pipe string; coengageable impact surfaces adapted to engage one another in at least one of said contracted and extended positions; first chamber means between said members hydraulic means enclosed by said first chamber means for releasably retarding relative movement of said members; second chamber means between said members separate from said first chamber means; means on said mandrel and housing members enclosed by said second chamber means for slidably and corotatively coupling said members together; said first chamber means being filled with a hydraulic fluid having a substantially constant viscosity over a wide temperature range; said second chamber means being filled with a lubricant adapted to prevent wear on said members; and balancing means for each of said first and second chamber means to equalize pressures therein with the hydrostatic pressure of the fluids in a well bore.

2. A jar apparatus comprising: an inner tubular member telescopically disposed within an outer tubular member; means for connecting each of said members to a pipe string; limit means for stopping telescoping movement of said members in longitudinally spaced positions; first chamber means between said members filled with a hydraulic fluid; hydraulically operable means in said first chamber for retarding relative movement only over an initial portion of the relative movement of said members, said hydraulic means then enabling free telescoping movement over the remaining portion of such movement; second chamber means between Said members filled with a lubricant; spline means totally disposed within said second chamber means for preventing rotation of one member relative to the other; and seal means between said members at the ends of each of said chambers, the respective seal means for each chamber being located on the same seal diameter to provide constant volume for the respective chambers during telescopic movement of said members.

3. The jar apparatus of claim 2 further including means for balancing the pressure within said first and second chamber means with the hydrostatic pressure of fluids in a well bore.

4. The jar apparatus of claim 3 wherein said balancing means includes a first balance piston movable between said members and having one face forming a wall of said first chamber means and the other face exposed to fluid pressure in a well bore, and a second balance piston between said members and having one face forming a wall of said second chamber means and the other face thereof exposed to fluid pressure in a well bore.

5. A well jar apparatus comprising: a housing assembly having a cylinder section, longitudinally spaced seal sections and a spline section; a mandrel assembly telescopically disposed within said housing assembly and including a cylinder section and a spline section; coengageable impact surfaces on said housing and mandrel assembly adapted to be bought together to deliver an impact blow to an object stuck in a well bore; first chamber means between said cylinder sections; hydraulic fluid filling said first chamber means; first seal means on one of said seal sections sealingly slidable on one of said cylinder cylinder sections for closing the other end of said 'first chamber means and for equalizing the fluid pressure in said first chamber means with hydrostatic pressure of fluids in a well bore; hydraulically operable means in said first chamber means having portions cooperating with said cylinder sections for retarding relative longitudinal movement only over an initial portion of the movement of said mandrel and housing assemblies; second chamber means between said mandrel and housing assemblies; a lubricant filling said second chamber means; second seal means on the other of said seal sections sealingly slidable on one of said spline sections for closing one end of said second chamber means; second pressure transmitting means sealingly slidable between said spline sections and closing the other end of said second chamber means, said second pressure transmitting means functioning to equalize fluid pressure in saidsecond chamber means with the hydrostatic pressure of fluids in a well bore; and longitudinally ex tending splines on said spline sections in said second chamber means for preventing relative rotation of said mandrel and housing assemblies while enabling relative longitudinal movement thereof.

6. The apparatus'of claim 5 wherein respective pressure transmitting means are sealingly slidab'le on the same seal diameters as the respective seal means closing one end of said chamber means to provide respective constant volumes for said chamber means during telescoping movement of said mandrel and housing assemblies. 

1. A jar apparatus comprising: a mandrel member telescopically disposed within a housing member, said members being relatively movable between extended and contracted positions; means for connecting said members in a pipe string; coengageable impact surfaces adapted to engage one another in at least one of said contracted and extended positions; first chamber means between said members; hydraulic means enclosed by said first chamber means for releasably retarding relative movement of said members; second chamber means between said members separate from said first chamber means; means on said mandrel and housing members enclosed by said second chamber means for slidably and corotatively coupling said members together; said first chamber means being filled with a hydraulic fluid having a substantially constant viscosity over a wide temperature range; said second chamber means being filled with a lubricant adapted to prevent wear on said members; and balancing means for each of said first and second chamber means to equalize pressures therein with the hydrostatic pressure of the fluids in a well bore.
 2. A jar apparatus comprising: an inner tubular member telescopically disposed within an outer tubular member; means for connecting each of said members to a pipe string; limit means for stopping telescoping movement of said members in longitUdinally spaced positions; first chamber means between said members filled with a hydraulic fluid; hydraulically operable means in said first chamber for retarding relative movement only over an initial portion of the relative movement of said members, said hydraulic means then enabling free telescoping movement over the remaining portion of such movement; second chamber means between said members filled with a lubricant; spline means totally disposed within said second chamber means for preventing rotation of one member relative to the other; and seal means between said members at the ends of each of said chambers, the respective seal means for each chamber being located on the same seal diameter to provide constant volume for the respective chambers during telescopic movement of said members.
 3. The jar apparatus of claim 2 further including means for balancing the pressure within said first and second chamber means with the hydrostatic pressure of fluids in a well bore.
 4. The jar apparatus of claim 3 wherein said balancing means includes a first balance piston movable between said members and having one face forming a wall of said first chamber means and the other face exposed to fluid pressure in a well bore, and a second balance piston between said members and having one face forming a wall of said second chamber means and the other face thereof exposed to fluid pressure in a well bore.
 5. A well jar apparatus comprising: a housing assembly having a cylinder section, longitudinally spaced seal sections and a spline section; a mandrel assembly telescopically disposed within said housing assembly and including a cylinder section and a spline section; coengageable impact surfaces on said housing and mandrel assembly adapted to be bought together to deliver an impact blow to an object stuck in a well bore; first chamber means between said cylinder sections; hydraulic fluid filling said first chamber means; first seal means on one of said seal sections sealingly slidable on one of said cylinder sections for closing one end of said first chamber means; first pressure transmitting means sealingly slidable between said cylinder sections for closing the other end of said first chamber means and for equalizing the fluid pressure in said first chamber means with hydrostatic pressure of fluids in a well bore; hydraulically operable means in said first chamber means having portions cooperating with said cylinder sections for retarding relative longitudinal movement only over an initial portion of the movement of said mandrel and housing assemblies; second chamber means between said mandrel and housing assemblies; a lubricant filling said second chamber means; second seal means on the other of said seal sections sealingly slidable on one of said spline sections for closing one end of said second chamber means; second pressure transmitting means sealingly slidable between said spline sections and closing the other end of said second chamber means, said second pressure transmitting means functioning to equalize fluid pressure in said second chamber means with the hydrostatic pressure of fluids in a well bore; and longitudinally extending splines on said spline sections in said second chamber means for preventing relative rotation of said mandrel and housing assemblies while enabling relative longitudinal movement thereof.
 6. The apparatus of claim 5 wherein respective pressure transmitting means are sealingly slidable on the same seal diameters as the respective seal means closing one end of said chamber means to provide respective constant volumes for said chamber means during telescoping movement of said mandrel and housing assemblies. eeeeeeeeee8ssssssssss 